Initially, it's a light based version, but I'm looking to create a dark version too.

There are some areas that I couldn't fully address in the theme, either because I haven't worked out how to access styling a feature, or it may not be exposed by the theme system. The white button text on the Find / Replace buttons being a good example of something I couldn't find a rule for, or changing the "Bookmark" and "Mark" gutter images.